Plastic single-axis zero-expansion composite material and preparation method thereof

ABSTRACT

A plastic single-axis zero-expansion composite material and a preparation method thereof are provided, featuring incorporating an α-Fe second phase into a matrix of R 2 Fe 17 -type intermetallic compound, in which R refers to a rare earth element with a low atomic content of 4%. The material has simple synthesis steps and can be easily implemented, and the phase interface formed by the eutectic reaction is more stable than the composite structures obtained by the traditional solid-phase sintering, thereby realizing the regulation of the thermal expansion, and significantly improving the mechanical properties.

CROSS-REFERENCE TO THE RELATED APPLICATIONS

This application is based upon and claims priority to Chinese PatentApplication No. 201911319876.1, filed on Dec. 19, 2019; the disclosureof which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of high-precisioninstruments, and particularly relates to a plastic single-axiszero-expansion composite material and preparation method thereof.

BACKGROUND

Zero-expansion materials, as a functional material, refer to materialswhose dimensions do not vary with the temperature, even to a littleextent. They are mainly applied to the fields of high-precisioninstruments, such as optical instrument, microelectronic devices andaerospace. Currently, materials whose shapes and dimensions do not varywith the temperature are urgently needed, to guarantee that themanufactured members have a high dimensional stability, a high precisionand a long service life. Low (near zero)-thermal-expansion materialshave microscopic dimensions that are approximately constant with thevariation of the temperature, and can maintain a volume that does notexpand or contract within particular temperature intervals. Therefore,the study on such a type of materials is being paid increasingly moreattention.

Zero-expansion materials may be generally classified into three types,ceramics, metallic materials and composites. Ceramic materials have poormechanical properties and exhibit no outstanding property in thermalconduction or electric conduction, which makes them not promotable andapplicable in a large scale. Although metallic materials have excellentproperties in thermal conduction and electric conduction, there are rarematerials among them that have the zero-expansion property, which aremainly intermetallic compounds. However, the inherent brittleness of theintermetallic compounds themselves makes them not applicable in a largescale. Traditional composite materials are generally metal/ceramic-basedcomposite zero-expansion materials prepared by solid-phase sintering.However, such compounding improves the mechanical properties to alimited extent, and the mismatching between the thermal-expansionproperties of the two materials themselves results in hot cracks andthus failure.

Therefore, it is necessary to develop a plastic single-axiszero-expansion composite material that has a high strength andpreparation method thereof, to overcome the disadvantages of the priorart, to solve or alleviate one or more of the above problems.

SUMMARY

In view of that, the present disclosure provides a plastic single-axiszero-expansion composite material and preparation method thereof, byincorporating an a-Fe second phase into a matrix of R₂Fe₁₇-typeintermetallic compound, wherein R refers to a rare earth element. Thematerial has simple synthesis steps and can be easily implemented, andthe phase interface formed by the eutectic reaction is more stable thanthe composite structures obtained by the traditional solid-phasesintering, which realizes the regulation of the thermal expansion, andsignificantly improves the mechanical properties.

In an aspect, the present disclosure provides a preparation method of aplastic single-axis zero-expansion composite material, wherein thepreparation method incorporates an α-Fe phase as a second phase into anR₂Fe₁₇-type intermetallic compound, wherein the R₂Fe₁₇ exhibits negativethermal expansion, the α-Fe exhibits positive thermal expansion, and thesingle-axis zero-expansion composite material having a wide temperaturezone is obtained by regulating the positive thermal expansion and thenegative thermal expansion by controlling a ratio of the two phases andan orientation of the R₂Fe₁₇, wherein R is a rare earth element.

In an embodiment according to the above aspect and among potentialembodiments, the preparation method comprises the steps of:

step 1: providing a raw material of the R₂Fe₁₇-type intermetalliccompound and a raw material of the α-Fe phase;

step 2: mixing the two raw materials of the step 1;

step 3: smelting uniformly the mixed raw materials by using anelectric-arc furnace;

step 4: annealing the uniformly smelted sample under a protectiveatmosphere; and

step 5: after the annealing has ended, obtaining the single-axiszero-expansion composite material.

In an embodiment according to the above aspect and among potentialembodiments, the water tanks are evenly distributed or periodicallydistributed on the copper plate.

In an embodiment according to the above aspect and among potentialembodiments, in the step 1 both of purities of the raw material of theR₂Fe₁₇-type intermetallic compound and the raw material of the α-Fephase are >99.5%.

In an embodiment according to the above aspect and among potentialembodiments, in the step 1 the R₂Fe₁₇ phase is of a hexagonal crystalsystem or a trigonal crystal system, wherein when R is a light rareearth element, R is of a trigonal crystal system, and has a space groupof R-3m, and when R is a heavy rare earth element, R is of a hexagonalcrystal system, and has a space group of P6₃/mmC.

In an embodiment according to the above aspect and among potentialembodiments, the step 4 comprises placing the obtained sample under theprotective atmosphere, and annealing at 1100° C. for at least 24 h,wherein the protective atmosphere is vacuum or an inert gas.

In an embodiment according to the above aspect and among potentialembodiments, the R₂Fe₁₇-type intermetallic compound is a matrix phase,the α-Fe phase is a plastic second phase, and the plastic second phaseis incorporated to improve a mechanical behavior of the matrix phase,and by synergy between the two phases, inhibit an intrinsic brittlenessof the intermetallic compound.

According to the above aspect, there is further provided a plasticsingle-axis zero-expansion composite material, wherein a chemicalformula of the single-axis zero-expansion composite material isR_(x)Fe_(1-x), wherein 0<x≤0.09, and R is a rare earth element.

In an embodiment according to the above aspect and among potentialembodiments, a same copper plate has an average taper change rate of thetaper of 0.5%-2.5% in the entire length.

In an embodiment according to the above aspect and among potentialembodiments, the single-axis zero-expansion composite material comprisesHo_(0.04)Fe_(0.96), and the Ho_(0.4)Fe_(0.96) exhibits a characteristicof zero expansion within a temperature interval of 100-335 K, wherein acoefficient of linear expansion α₁ is 0.19×10⁻⁶.

As compared with the prior art, the present disclosure can obtain thefollowing technical effects:

1. The high-strength zero-expansion composite material according to thepresent disclosure has shapes and dimensions that do not vary with thetemperature, and has a high dimensional stability, a high precision anda long service life. The low (near zero)-thermal-expansion material hasmicroscopic dimensions that are approximately constant with thevariation of the temperature, and can maintain a volume that does notexpand or contract within particular temperature intervals.

2. The zero-expansion composite material according to the presentdisclosure is a zero-expansion composite material that has excellentmechanical properties, which overcomes the intrinsic brittleness oftraditional intermetallic compounds, and has higher thermal conductivityand electric conductivity than those of conventional ceramic materials.Furthermore, the raw materials are more inexpensive than intermetalliccompounds, which enables the large-scaled application of the compositematerial.

Certainly, the implementation of either product according to the presentdisclosure may not necessarily achieve all of the above-describedtechnical effects.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly describe the technical solutions of theembodiments of the present disclosure, the drawings that are required tobe used in the embodiments will be described below briefly. Apparently,the drawings described below are merely some of the embodiments of thepresent disclosure, and a person skilled in the art can obtain otherdrawings according to those drawings without paying creative work.

FIG. 1 is a finely finished X-ray diffraction pattern of the powder ofHo_(0.04)Fe_(0.96), one of the zero-expansion composite materialaccording to the present disclosure when R=Ho, at 300 K;

FIG. 2 is diagrams of the crystal structures of the R₂Fe₁₇ phase and theα-Fe phase according to the present disclosure;

FIG. 3 is plots of the linear expansion of the R_(x)Fe_(1-x) (R=Ho, andx=0.03, 0.04, 0.05, 0.07 and 0.09) according to the present disclosure;and

FIG. 4 is an engineering stress-strain curve of the Ho_(0.04)Fe_(0.96)according to the present disclosure at 300 K.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to better understand the technical solutions of the presentdisclosure, the embodiments of the present disclosure will be describedbelow in detail with reference to the drawings.

It should be understood that the described embodiments are merely someof the embodiments of the present disclosure, and are not all of theembodiments. All of the other embodiments that a person skilled in theart obtains on the basis of the embodiments in the present disclosurewithout paying creative work fall within the protection scope of thepresent disclosure.

The terms used in the embodiments of the present disclosure are merelyfor the purpose of describing the particular embodiments, and are notintended to limit the present disclosure. The terms “a”, “an”, “said”and “the” used in the singular forms in the embodiments and the appendedclaims of the present disclosure are intended to encompass the pluralforms, unless expressly indicated otherwise in the context.

The present disclosure provides a plastic single-axis zero-expansioncomposite material. A chemical formula of the single-axis zero-expansioncomposite material is R_(x)Fe_(1-x), wherein 0<x≤0.09, and R is a rareearth element. The single-axis zero-expansion composite materialcomprises Ho_(0.04)Fe_(0.96), and the Ho_(0.04)Fe_(0.96) exhibits acharacteristic of zero expansion within a temperature interval of100-335 K, wherein a coefficient of linear expansion α₁ is 0.19×10⁻⁶.

The present disclosure further provides a preparation method of aplastic single-axis zero-expansion composite material, wherein thepreparation method incorporates an α-Fe phase as a second phase into anR₂Fe₁₇-type intermetallic compound, wherein the R₂Fe₁₇ exhibits negativethermal expansion, the α-Fe exhibits positive thermal expansion, and theplastic single-axis zero-expansion composite material having a widetemperature zone is obtained by regulating the positive thermalexpansion and the negative thermal expansion by controlling a ratio ofthe two phases and an orientation of the R₂Fe₁₇.

The preparation method comprises the steps of:

step 1: providing a raw material of the R₂Fe₁₇-type intermetalliccompound and a raw material of the α-Fe phase, wherein both of thepurities of the raw materials are >99.5%, the R₂Fe₁₇ phase is of ahexagonal crystal system or a trigonal crystal system, wherein when R isa light rare earth element, R is of a trigonal crystal system, and has aspace group of R-3m, and when R is a heavy rare earth element, R is of ahexagonal crystal system, and has a space group of P6₃/mmC, and the α-Fephase is of a cubic crystal system, and has a space group of Im-3m;

step 2: mixing the two raw materials of the step 1;

step 3: smelting uniformly the mixed raw materials by using anelectric-arc furnace;

step 4: placing the obtained uniformly smelted sample under a protectiveatmosphere, and annealing at 1100° C. for at least 24 h, wherein theprotective atmosphere is vacuum or an inert gas; and

step 5: after the annealing has ended, obtaining the single-axiszero-expansion composite material.

In the preparation method according to the present disclosure, theR₂Fe₁₇-type intermetallic compound is a matrix phase, the α-Fe phase isa plastic second phase, and the plastic second phase is incorporated toimprove a mechanical behavior of the matrix phase, and by synergybetween the two phases, effectively inhibit the intrinsic brittleness ofthe intermetallic compound, and realize a great improvement on themechanical properties.

Example 1

A block of the single-axis zero-expansion composite material accordingto the present disclosure, in which the composition isHo_(0.04)Fe_(0.96), was synthesized by using the electric-arc-furnacesmelting process, wherein the reaction equation is as follows:

0.04×Ho+0.96Fe=Ho_(0.04)Fe_(0.96)

The particular operation was performed according to the following steps:

10 g of the raw materials of Ho and Fe at the molar ratio of 0.04:0.96was weighed. The raw materials were placed into an electric-arc furnace,the furnace was vacuumed (to the vacuum degree of <2.5×10⁻³ Pa), andunder that vacuum condition or the protection of an inert gas the systemwas smelted for 3 times for 1 min each time, which may optionally beassisted by electromagnetic stirring to homogenize the alloy. Theobtained sample was placed under vacuum or an inert atmosphere andannealed at 1100° C. for at least 24 h. The result of X-ray diffractionindicated that the obtained product is of an Ho_(0.04)Fe_(0.96)composite phase, and has no impurity.

Example 2

A block of the single-axis zero-expansion composite material accordingto the present disclosure, in which the composition isE_(r0.04)Fe_(0.96), was synthesized by using the electric-arc-furnacesmelting process, wherein the reaction equation is as follows:

0.04×Er+0.96Fe=E_(r0.04)Fe_(0.96)

The particular operation was performed according to the following steps:

10 g of the raw materials of Er and Fe at the molar ratio of 0.04:0.96was weighed. The raw materials were placed into an electric-arc furnace,the furnace was vacuumed (to the vacuum degree of <2.5×10⁻³ Pa), andunder that vacuum condition or the protection of an inert gas the systemwas smelted for 3 times for 1 min each time, which may optionally beassisted by electromagnetic stirring to homogenize the alloy. Theobtained sample was placed under vacuum or an inert atmosphere andannealed at 1100° C. for at least 24 h. The result of X-ray diffractionindicated that the obtained product is of an E_(r0.04)Fe_(0.96)composite phase, and has no impurity.

The zero-expansion material Ho_(0.04)Fe_(0.96) that was obtained inExample 1 was measured with respect to the linear expansion, and itexhibits the characteristic of zero expansion within the temperatureinterval of 100-335 K, wherein the coefficient of linear expansion (cu)is 0.19×10⁻⁶. Furthermore, its mechanical properties were measured, andit exhibits excellent mechanical properties, wherein its yield strengthreaches 700 Mpa, and its plastic elongation is up to 15%.

FIG. 1 is a finely finished X-ray diffraction pattern of the powder ofHo_(0.04)Fe_(0.96), one of the zero-expansion composite materialaccording to the present disclosure when R=Ho, at 300 K. It can be seenfrom the pattern that the X-ray diffraction pattern that was simulatedbased on its crystal structure and the X-ray diffraction patternobtained in the experiment were consistent, which proves the correctnessof the structural model of the zero-expansion composite materialaccording to the present disclosure.

FIG. 2 is diagrams of the crystal structures of the R₂Fe₁₇ phase and theα-Fe phase according to the present disclosure. The crystal structuresaccording to the present disclosure are hexagonal phase or trigonalphase of the rare-earth rich R₂Fe₁₇ type, and the body-centered cubicphase formed by the single Fe element.

FIG. 3 is plots of the linear expansion of the R_(x)Fe_(1-x) (R=Ho, andx=0.03, 0.04, 0.05, 0.07 and 0.09) according to the present disclosure.From the linear-expansion curve of the Ho_(x)Fe_(1-x) according to thepresent disclosure, it can be known that regulating the molar ratio ofHo:Fe can realize the regulation of the thermal expansion from negativeto positive, and at the composition of Ho_(0.04)Fe_(0.96) it exhibitsthe characteristic of zero expansion, wherein at 100-335 K thecoefficient of thermal expansion is 0.19×10⁻⁶.

FIG. 4 is an engineering stress-strain curve of the Ho_(0.04)Fe_(0.96)according to the present disclosure at 300K. From the engineeringstress-strain curve according to the present disclosure, it can be knownthat the zero-expansion composite material exhibits excellent mechanicalproperties, wherein its yield strength reaches 700 Mpa, and its plasticelongation is up to 15%.

The above description describes in detail the plastic single-axiszero-expansion composite material and preparation method thereofaccording to the embodiments of the present application. The descriptionof the above embodiments is merely intended to facilitate to understandthe method according to the present application and its core concept.Moreover, for a person skilled in the art, on the basis of the conceptof the present application, the particular embodiments and the range ofapplication may be varied. In conclusion, the contents of thedescription should not be understood as limiting the presentapplication.

The description and the claims employ certain words to refer toparticular elements. A person skilled in the art should understand thathardware manufacturers may use different nouns to refer to the same oneelement. The description and the claims do not distinguish the elementsaccording to the difference of the names, but use the difference in thefunctions of the elements as the criteria of distinguishing. Forexample, throughout the description and the claims the “comprise” andthe “include” are open-ended terms, so they should be interpreted as“including but not limited to”. The “substantially” refers to that,within an acceptable range of error, a person skilled in the art can,within the range of error, solve the technical problem and essentiallyreach the technical effects. The subsequent description is thepreferable embodiments of the present application, but the descriptionis for the purpose of explaining the general principle of the presentapplication, and is not intended to limit the scope of the presentapplication. The protection scope of the present application should bedefined by the appended claims.

It should also be noted that the terms “comprise” and “include” or anyvariants thereof are intended to encompass non-exclusive inclusions, sothat a product or system comprising a series of elements does not onlycomprise those elements, but also further comprises other elements notexplicitly listed, or further comprises elements that are inherent tosuch a product or system. Unless further limitation is set forth, anelement defined by the wording “comprising a . . . ” does not excludeadditional the same element in the product or system comprising theelement.

It should be understood that the term “and/or” as used herein is merelythe description on the associated relation of associated objects, andindicates the existence of three relations. For example, A and/or B mayindicate the sole existence of A, the sole existence of B and theexistence of both of A and B. In addition, the symbol “/” as used hereingenerally refers to that the preceding and subsequent associated objectsare of a relation of “or”.

The above description illustrates and describes some preferableembodiments of the present application. However, as stated above, itshould be understood that the present application is not limited to theforms disclosed herein, and should not be deemed as the exclusion ofother embodiments. Instead, the present application may be used forvarious other combinations, modifications and circumstances, and can bemodified within the scope of the concept of the present application byemploying the above teaching or the techniques and knowledge in therelevant fields. Moreover, any modification or variation made by aperson skilled in the art does not depart from the spirit and scope ofthe present application, and should fall within the protection scope ofthe appended claims of the present application.

What is claimed is:
 1. A preparation method of a plastic single-axiszero-expansion composite material, wherein the preparation methodincorporates an α-Fe phase as a second phase into an R₂Fe₁₇-typeintermetallic compound, wherein the R₂Fe₁₇-type intermetallic compoundexhibits negative thermal expansion, the α-Fe phase exhibits positivethermal expansion; and the plastic single-axis zero-expansion compositematerial having a wide temperature zone is obtained by regulating thepositive thermal expansion and the negative thermal expansion bycontrolling a ratio of the α-Fe phase and the R₂Fe₁₇-type intermetalliccompound, and an orientation of the R₂Fe₁₇-type intermetallic compound,wherein R is a rare earth element.
 2. The preparation method accordingto claim 1, wherein the preparation method comprises the followingsteps: step 1: providing two raw materials: a raw material of theR₂Fe₁₇-type intermetallic compound and a raw material of the α-Fe phase;step 2: mixing the two raw materials of the step 1 into mixed rawmaterials; step 3: smelting uniformly the mixed raw materials of step 2to form a uniformly smelted sample by using an electric-arc furnace;step 4: annealing the uniformly smelted sample of step 3 under aprotective atmosphere; and step 5: after the annealing of step 4 hasended, obtaining the plastic single-axis zero-expansion compositematerial.
 3. The preparation method according to claim 2, wherein in thestep 1, purities of the raw material of the R₂Fe₁₇-type intermetalliccompound and the raw material of the α-Fe phase are both >99.5%.
 4. Thepreparation method according to claim 2, wherein in the step 1, theR₂Fe₁₇-type intermetallic compound is of a hexagonal crystal system or atrigonal crystal system, wherein when R is a light rare earth element,the R₂Fe₁₇-type intermetallic compound is of a trigonal crystal system,and has a space group of R-3m, and when R is a heavy rare earth element,the R₂Fe₁₇-type intermetallic compound is of a hexagonal crystal system,and has a space group of P6₃/mmC.
 5. The preparation method according toclaim 2, wherein in the step 1 the α-Fe phase is of a cubic crystalsystem and has a space group of Im-3m.
 6. The preparation methodaccording to claim 2, wherein the step 4 comprises placing the uniformlysmelted sample under the protective atmosphere, and annealing at 1100°C. for at least 24 h, wherein the protective atmosphere is vacuum or aninert gas.
 7. The preparation method according to claim 1, wherein theR₂Fe₁₇-type intermetallic compound is a matrix phase, the α-Fe phase isa plastic second phase, and the plastic second phase is incorporatedinto the matrix phase to improve a mechanical behavior of the matrixphase, and by synergy between the matrix phase and the plastic secondphase, inhibit an intrinsic brittleness of the R₂Fe₁₇-type intermetalliccompound.
 8. A plastic single-axis zero-expansion composite material,prepared by using the preparation method according to claim 1, wherein achemical formula of the single-axis zero-expansion composite material isR_(x)Fe_(1-x), wherein 0<x≤0.09, and R is a rare earth element.
 9. Theplastic single-axis zero-expansion composite material according to claim8, wherein the single-axis zero-expansion composite material comprisesHo_(0.04)Fe_(0.96), and the Ho_(0.04)Fe_(0.96) exhibits a characteristicof zero expansion within a temperature interval of 100-335K, wherein acoefficient of linear expansion α₁ is 0.19×10⁻⁶.
 10. The plasticsingle-axis zero-expansion composite material according to claim 8,wherein the preparation method comprises the following steps: step 1:providing two raw materials: a raw material of the R₂Fe₁₇-typeintermetallic compound and a raw material of the α-Fe phase; step 2:mixing the two raw materials of the step 1 into mixed raw materials;step 3: smelting uniformly the mixed raw materials of step 2 to form auniformly smelted sample by using an electric-arc furnace; step 4:annealing the uniformly smelted sample of step 3 under a protectiveatmosphere; and step 5: after the annealing of step 4 has ended,obtaining the plastic single-axis zero-expansion composite material. 11.The plastic single-axis zero-expansion composite material according toclaim 10, wherein in the step 1, purities of the raw material of theR₂Fe₁₇-type intermetallic compound and the raw material of the α-Fephase are both >99.5%.
 12. The plastic single-axis zero-expansioncomposite material according to claim 10, wherein in the step 1, theR₂Fe₁₇-type intermetallic compound is of a hexagonal crystal system or atrigonal crystal system, wherein when R is a light rare earth element,the R₂Fe₁₇-type intermetallic compound is of a trigonal crystal system,and has a space group of R-3m, and when R is a heavy rare earth element,the R₂Fe₁₇-type intermetallic compound is of a hexagonal crystal system,and has a space group of P6₃/mmC.
 13. The plastic single-axiszero-expansion composite material according to claim 10, wherein in thestep 1 the α-Fe phase is of a cubic crystal system and has a space groupof Im-3m.
 14. The plastic single-axis zero-expansion composite materialaccording to claim 10, wherein the step 4 comprises placing theuniformly smelted sample under the protective atmosphere, and annealingat 100° C. for at least 24 h, wherein the protective atmosphere isvacuum or an inert gas.
 15. The plastic single-axis zero-expansioncomposite material according to claim 8, wherein the R₂Fe₁₇-typeintermetallic compound is a matrix phase, the α-Fe phase is a plasticsecond phase, and the plastic second phase is incorporated into thematrix phase to improve a mechanical behavior of the matrix phase, andby synergy between the matrix phase and the plastic second phase,inhibit an intrinsic brittleness of the R₂Fe₁₇-type intermetalliccompound.